JPH08197212A - Method for continuously casting molten metal and mold for continuous casting - Google Patents

Abstract

PURPOSE: To improve the quality of a cast slab by making the density distributions of magnetic flux and induction current generated near a meniscus part suitable and controlling the solidified shell shape at the initial stage. CONSTITUTION: Molten metal is poured into an electric conductive mold for continuous casting formed with one pair of long side plates 6 and short side plates. While controlling the shell shape at the initial stage by directly conducting the electric power in the vertical direction of the mold to impress AC magnetic field near the meniscus 3, the casting is executed. Then, slits 1 are formed in the vertical direction and thickness direction of the long side plates 6 over the meniscus 3 corresponding part from the upper ends of the long side plates 6. The density distributions of the magnetic flux and the induction current generated near the meniscus part 3 are made to be suitable by adjusting number of the divisions and/or the dividing width and adjusting the current to each divided part of the long side plate 6 electrically divided with the slits 1 while using the variable resistance 7, etc., to control the shape of the solidified shell at the initial stage. By this method, the impressed efficiency of the magnetic field can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to continuous casting of molten metal using an alternating magnetic field, and in particular, by suitably controlling the shape of an initially solidified shell produced in a mold, high-speed casting with improved slab quality. The present invention proposes a continuous casting method and a continuous casting mold that enable the above.

[0002]

2. Description of the Related Art Heretofore, as a technique for controlling the shape of an initial solidified shell using an alternating magnetic field, for example, Japanese Patent Publication No.
There are means proposed and disclosed in JP-A-7-21408 (casting method for molten metal) and JP-A-64-83348 (powder feeding method in continuous casting).

However, in these means, since the electromagnetic induction coil is installed on the outside of the mold backup plate, the backup plate and the mold are induction-heated, and the distance between the electromagnetic induction coil and the initial solidification shell is large. As a result, the efficiency of applying the magnetic field is extremely poor, the power loss increases, and the magnetic field applying capability is limited. This tendency becomes more remarkable as the frequency of the applied magnetic field becomes higher, and it is virtually impossible to control the shape of the initial solidified shell by the magnetic field in the high frequency region of 1 kHz or higher.

As a technique for solving such a problem, there is a means disclosed in JP-A-4-100658 (mold for continuous casting). This means applies an alternating current directly to the mold in the lateral direction, and since the mold plays the role of an electromagnetic induction coil, there is no shielding of the magnetic field by the mold or the backup plate and there is no gap with the initial solidification shell. Therefore, there is an advantage that the magnetic field application efficiency is increased.

However, this means has a problem that the magnetic field cannot be efficiently applied only to the initial solidified shell portion due to the current flowing through the entire mold, and the application efficiency is reduced.

In other words, the theory of electronics A. Volume 110, Issue 9, p
As shown in 591-597 (1992), when an alternating current is applied to a conductor plate, the current and the magnetic field generated by the current itself cause the current to flow at both ends as shown in Fig. 1. There is a phenomenon that the magnetic field concentrates on the edge part, and this tendency becomes more remarkable as the frequency becomes higher. Therefore, it was difficult to apply the magnetic field appropriately and efficiently to the initial solidified shell part.

FIG. 1 is an explanatory diagram showing a current density distribution when electricity is applied in the left-right direction of the mold plate.

[0008]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems in an advantageous manner, and efficiently optimizes the density distribution of magnetic flux and induced current so as to optimize the shape of the initial solidified shell. The object of the present invention is to propose a continuous casting method for molten metal and a casting mold for continuous casting, which can be controlled in a constant manner.

[0009]

According to the present invention, as a result of investigating a current density distribution flowing through a flat plate by measuring a magnetic flux density generated on the surface thereof, an AC current flowing through the flat plate has a shorter current path. It was achieved by the knowledge that the tendency to concentrate on the edge part decreases and that the current density distribution can be changed by changing the position of the terminals when multiple terminals are provided on opposite ends of the flat plate. is there. That is, the gist of the present invention is as follows.

The molten metal is poured into a conductive continuous casting mold consisting of a pair of long side plates and short side plates, and an alternating magnetic field is applied in the vicinity of the meniscus by directly energizing the mold vertically. A continuous casting method for molten metal in which the shape of a solidified shell is controlled while controlling the shape of a solidified shell, and has a slit in the vertical direction and the thickness direction of the long side plate from the upper end of the long side plate to a portion corresponding to the meniscus, and the slit electrically By adjusting the number of divisions and / or the division width of the long side plate that is divided into two and adjusting the amount of current to each division side, the density distribution of the magnetic flux and induced current generated near the meniscus is optimized, and the initial solidification shell It is a continuous casting method for molten metal, characterized by controlling the shape.

The molten metal is poured into a conductive continuous casting mold consisting of a pair of long side plates and short side plates, and an alternating magnetic field is applied in the vicinity of the meniscus by directly energizing the mold in the vertical direction. A method for continuous casting of molten metal in which the shape of the solidified shell is controlled, in which the distribution of the current density flowing in the mold can be changed by changing the number and position of the AC current terminals provided in the portion corresponding to the lower portion of the meniscus of the long side plate. This is a continuous casting method for molten metal, characterized by adjusting the density distribution of magnetic flux and induced current generated near the meniscus to control the shape of the initial solidified shell.

A conductive continuous casting mold comprising a pair of a long side plate and a short side plate, wherein the long side plate extends vertically from the upper end to a portion immediately above the meniscus and has a long side plate thickness. A continuous molten metal that has one or more slits in the direction and is provided with an AC current terminal at each upper end electrically divided by the slits and an AC current terminal at the lower end of the long side plate. It is a casting mold.

A conductive continuous casting mold comprising a pair of a long side plate and a short side plate, wherein the long side plate has one or more current-carrying holes in the lateral direction corresponding to the lower portion of the meniscus. A casting mold for continuous casting of molten metal, wherein an alternating current terminal is provided in the energization hole and an alternating current terminal is provided at an upper end of the long side plate.

A conductive continuous casting mold comprising a pair of a long side plate and a short side plate, wherein the long side plate extends from the upper end to a portion immediately above the meniscus in the vertical direction and the thickness of the long side plate. Direction has one or more slits, and an AC current terminal is provided at each upper end portion electrically divided by the slits, and one or more current-carrying holes and one or more current-carrying holes are provided in the left-right direction of the portion corresponding to the lower part of the meniscus. It is a mold for continuous casting of molten metal in which holes have alternating current terminals of the same phase.

Here, by providing a slit on the long side plate of the mold and electrically dividing it, the insulation at this slit part causes the current to be biased to the left and right as the energizing distance from the upper end of the long side plate becomes longer. This is because it has the effect of preventing the movement. Further, in order to prevent a slag and a scratch of the slit from being generated on the slab by providing the slit, the lower end of the slit is preferably located above the meniscus.

[0016]

The operation of the present invention will be described below. This invention injects a molten metal into a conductive continuous casting mold consisting of a pair of long side plates and short side plates, respectively, and applies an alternating current directly in the vertical direction of the mold to generate an alternating magnetic field near the meniscus. When continuously casting the molten metal while controlling the shape of the initial solidified shell by applying, the portion corresponding to above the meniscus of the mold long side plate is electrically divided,
Unlike the case where the long side plate is not electrically divided, the current density does not greatly decrease at the edge part of the long side plate and extremely decreases at the center part, and the density distribution of magnetic flux and induced current can be optimized. As a result, the quality of the slab is improved over the entire width, and at the same time, stable high speed casting is possible.

Further, in the above, by adjusting the number of electrical divisions and / or the width of division and the amount of current to each division, the distribution of the current density flowing in the long side plate can be further optimized, and further The slab quality can be improved.

For the electrical division of the long side plate in the above, it is suitable to provide a slit in the vertical direction from the upper end to a portion immediately above the meniscus and in the thickness direction of the long side plate.

In addition, an AC current is passed between the AC current terminal provided at the upper end of the long side plate by providing an AC current hole in the portion corresponding to the lower portion of the meniscus of the long side plate and an AC current terminal in the hole for conduction. Further, by appropriately providing the current-carrying holes in the left-right direction, the quality of the slab can be improved in the same manner as described above, and since the magnetic field is applied predominantly to the initial solidified shell portion, the application efficiency of the magnetic field can be improved. It can be significantly improved.

In addition, when electrically dividing by the slit and providing a current-carrying hole are used in combination with each other, an extremely excellent magnetic field application efficiency can be obtained and a further slab quality can be obtained. It becomes possible to improve and further high speed casting.

[0021]

【Example】

Example 1 Explanation of the current density distribution in the long side plate obtained by measuring the magnetic flux density generated on the surface of the long side plate when energizing the mold long side plate conforming to the present invention in the air-core state The figures are shown in FIGS. In each of these figures, (a) is a front view and (b) is a side view.

FIG. 2 is an explanatory view showing the current density distribution in the long side plate of the mold which is electrically divided by providing slits in the vertical direction and the thickness direction of the long side plate from the upper end to a portion immediately above the meniscus.

FIG. 3 is a mold in which slits are provided in the vertical direction and in the thickness direction of the long side from the upper end to a portion immediately above the meniscus for electrical division, and a variable resistor for current adjustment is arranged in the division energizing path. It is explanatory drawing which shows the current density distribution in a long side plate. In this figure, the current-carrying hole is a blind hole because it is filled with an insulator, but it may be a through-hole. In this case, the diameter of the through-hole is 0.5 mm to prevent the occurrence of flaws on the surface of the slab due to the current-carrying hole. The following is recommended.

FIG. 4 is an explanatory view showing a current density distribution in a long side plate of a mold in which an energization hole is provided in a portion corresponding to a lower portion of a meniscus and an AC current terminal is provided in the energization hole.

In FIG. 5, slits are provided in the vertical direction from the upper end to a portion directly above the meniscus and in the thickness direction of the long side plate to electrically divide them, and an electrical conduction hole is provided in the portion corresponding to the lower portion of the meniscus and an alternating current is applied to the electrical conduction hole. It is explanatory drawing which shows the current density distribution in the long side plate of a mold which provided the terminal for electric current and arranged the variable resistance for electric current adjustment in the division | segmentation part electricity supply path.

In these figures, 1 is a slit, 2 is a terminal for alternating current, 3 is a meniscus, 4 is a hole for energization, 5 is a current path, 6 is a long side plate of a mold, 7 is a variable resistor, and 8 is a conductive wire. is there.

As is apparent from FIGS. 2 to 5, the current density distribution in the long side plate in the vicinity of the meniscus 3 does not become dense at both end edges thereof as shown in FIG. 1 and is equalized. ing.

Further, in these figures, in FIGS. 4 and 5 in which the meniscus lower part corresponding current carrying hole and the AC power supply terminal are provided in the current carrying hole, the current flows only in the part corresponding to the vicinity of the meniscus 3, so that the magnetic field It is obvious that the application efficiency is improved, and in FIG. 3 and FIG. 5 in which it is easy to adjust the number of divisions and / or the division width and the amount of current to each division,
It becomes easier to adjust the current density distribution, and thus it becomes easier to further optimize the density distribution of the magnetic flux and the induced current generated near the meniscus.

Example 2 The mold long side plate of the conventional example shown in FIG. 1 and the mold long side plate of the conforming example of the present invention shown in FIG. 5 were energized by using the same power source in an air-core state. FIG. 6 shows a summary of the results of measuring the magnetic flux density distribution on the surface of the long side plate width direction corresponding to the vicinity of the meniscus. FIG. 6 is a graph showing a magnetic flux density distribution in the long side plate width direction of the mold.

Here, the magnetic flux density distribution was obtained from the distribution of the electromotive force because the electromotive force measured by installing a search coil at each measurement location is proportional to the magnetic flux density. Note that FIG.
The magnetic flux density index of is represented by setting the maximum measured value to 1.

As is clear from FIG. 6, in the conventional example, the magnetic flux density distribution index is extremely lower in the central portion of the widthwise direction of the long side plate than at the both ends thereof, whereas the conformity example of the present invention. Shows a uniformly high value.

Example 3 As shown in FIG. 7, a pair of long side plates shown in FIG.
Continuous casting of steel was performed using a continuous casting mold consisting of a pair of short side plates (compliance example).

The casting conditions are shown below. Cross-sectional size of slab: 200mm (short side) x 1600mm (long side) Casting speed: 3m / min Power supply: Electric power --- 300kw, Frequency ---- 1kHz Steel type: Ultra low carbon steel [c] ≒ 0.01mass% )

Here, FIG. 7 is an explanatory view of a vertical section when steel is cast using a continuous casting mold conforming to the present invention.
1 is a slit, 2 is a terminal for alternating current, 3 is a meniscus,
4 is a hole for energization, 6 is a long side plate of the mold, 7 is a variable resistance, 8 is a conducting wire, 9 is a tundish 10 is an immersion nozzle, 11 is an initial solidification shell, 12 is a molten metal, 13 is powder, and 14 is an AC power supply. is there.

Although FIG. 7 shows the connection of AC power sources to the opposite long side plates in series, the cross section of the steel used in the continuous casting mold of FIG. It may be arranged in parallel as illustrated.

For comparison, continuous casting of steel was carried out in the same manner as above using the continuous casting mold having the long side plate shown in FIG. 1 (conventional example).

The slabs thus obtained were investigated for slab surface defects and sticking marks which may lead to breakout. The results of these investigations are shown in FIGS. 9 and 10, respectively.

FIG. 9 is a graph showing the surface defect generation index of the conventional example and the conforming example, and FIG. 10 is a graph showing the sticking mark generation index of the conventional example and the conforming example.

Here, the surface defect generation index indicates the ratio of defects such as cracks, dents, and blowholes per surface area of the slab, with the occurrence ratio in the conventional example being 1.

The sticking mark generation index is a ratio of the sticking marks generated per surface area of the slab, with the generation rate in the conventional example being 1.

As is clear from FIGS. 9 and 10, the surface defect generation index and the sticking mark generation index are greatly reduced in the conforming example of the present invention as compared with the conventional example.

[0042]

INDUSTRIAL APPLICABILITY The present invention, in continuous casting of molten metal, provides a slit at the upper end of the mold to electrically separate the mold when the shape of the initial solidified shell is controlled by directly energizing the mold in the vertical direction and / or By installing the current-carrying holes and terminals in the mold corresponding to the lower part of the meniscus, the density distribution of the current flowing through the mold is adjusted, and the density distribution of the appropriate magnetic flux and induced current is provided in the vicinity of the meniscus. If so, the shape of the initially solidified shell can be suitably controlled, and the quality of the obtained slab can be significantly improved. Furthermore, the efficiency of applying the magnetic field can be improved, which is extremely advantageous from the viewpoint of power saving.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a current density distribution when electricity is applied in the left-right direction of a mold plate.

FIG. 2 is an explanatory diagram showing a current density distribution in a long side plate of a mold, which is electrically divided by providing slits in a vertical direction and a thickness direction of the long side plate from a top end to a portion immediately above a meniscus.

FIG. 3 is a mold long side plate in which a slit is provided vertically from the upper end to a portion immediately above the meniscus and in the thickness direction of the long side plate for electrical division, and a variable resistor for current adjustment is arranged in the division energizing path. It is explanatory drawing which shows the current density distribution inside.

FIG. 4 is an explanatory diagram showing a current density distribution in a long side plate of a mold in which an energization hole is provided in a portion corresponding to a lower portion of a meniscus and an AC current terminal is provided in the energization hole.

FIG. 5 is a view in which a slit is provided in the vertical direction and in the thickness direction of the long side plate from the upper end to a portion directly above the meniscus to electrically divide, and a current-carrying hole is provided in a portion corresponding to the lower part of the meniscus and an AC current terminal is provided in the current-carrying hole. FIG. 3 is an explanatory view showing a current density distribution in a long side plate of a mold in which a variable resistance for current adjustment is arranged in a divided portion energization path.

FIG. 6 is a graph showing a magnetic flux density distribution index in the width direction of the long side plate of the mold.

FIG. 7 is an explanatory view of a vertical cross section when casting steel using a continuous casting mold that is compatible with the present invention. (AC power supply series connection)

FIG. 8 is an explanatory view of a vertical cross section when casting steel using a continuous casting mold that is compatible with the present invention. (AC power supply parallel connection)

FIG. 9 is a graph showing surface defect occurrence indexes of a conventional example and a compatible example.

FIG. 10 is a graph showing a stenking mark generation index of a conventional example and a compatible example.

[Explanation of symbols]

 1 Slit 2 AC Current Terminal 3 Meniscus 4 Energizing Hole 5 Current Path 6 Mold Long Side Plate 7 Variable Resistance 8 Conductor Wire 9 Tundish 10 Immersion Nozzle 11 Initial Solidification Shell 12 Molten Metal 13 Powder 14 AC Power Supply

Claims (5)

[Claims] 1. An alternating magnetic field is applied in the vicinity of a meniscus by injecting a molten metal into a conductive continuous casting mold that is composed of a pair of long side plates and short side plates, and by directly energizing the mold vertically. A method for continuous casting of molten metal in which the shape of the initially solidified shell is controlled by controlling the shape of the long side plate from the upper end to the portion corresponding to the meniscus in the vertical direction and in the thickness direction of the long side plate, and by the slit, By adjusting the number of divisions and / or the division width of the long side plate that is electrically divided and adjusting the amount of current to each division, the density distribution of the magnetic flux and induced current generated near the meniscus is optimized and initial solidification is performed. A continuous casting method for molten metal, which comprises controlling the shape of a shell. 2. An alternating magnetic field is applied in the vicinity of the meniscus by injecting a molten metal into a conductive continuous casting mold that is composed of a pair of long side plates and a short side plate, and directly energizing the mold vertically. This is a continuous casting method for molten metal in which the shape of the initial solidified shell is controlled while controlling the shape of the initial solidified shell.The current density flowing in the mold can be changed by changing the number and position of the AC current terminals provided in the portion corresponding to the bottom of the meniscus of the long side plate. A continuous casting method for molten metal, characterized by adjusting the distribution to optimize the density distribution of magnetic flux and induced current generated near the meniscus, and controlling the shape of the initial solidified shell. 3. A conductive continuous casting mold comprising a pair of a long side plate and a short side plate, wherein the long side plate extends from the upper end to a portion immediately above the meniscus in the vertical direction and the long side plate. Molten metal having one or more slits in the thickness direction and provided with an AC current terminal at each upper end portion electrically divided by the slit and an AC current terminal at the lower end of the long side plate. Continuous casting mold. 4. A conductive continuous casting mold comprising a pair of a long side plate and a short side plate, wherein the long side plate has one or more current-carrying holes in the lateral direction corresponding to the lower portion of the meniscus. A casting mold for continuous casting of molten metal, comprising an alternating current terminal provided in the energizing hole and an alternating current terminal provided at an upper end of the long side plate. 5. A conductive continuous casting mold comprising a pair of a long side plate and a short side plate, wherein the long side plate extends from the upper end to a portion directly above the meniscus in the vertical direction and the long side plate. There is one or more slits in the thickness direction, an AC current terminal is provided at each upper end portion electrically divided by the slits, and one or more current-carrying holes and one or more current-carrying holes in the left-right direction corresponding to the lower portion of the meniscus are provided. A mold for continuous casting of molten metal, in which terminals for alternating current of the same phase are provided in the current-carrying holes.